1. Field of the Invention
The present invention relates to an electrical junction box for use, for example, in establishing a relative connection between electric circuits in the form of a wire harness.
2. Related Art Statement
An electrical junction box is typically constructed constituted in such a manner that a plurality of circuit boards are stacked together and accommodated in a case, and connectors connectors are disposed on both the upper surface and the lower surface of the aforementioned case so as to be connected to the internal circuits. However, the number of the connectors formed on the two surfaces of the case is insufficient where an increase in the number of internal circuits is required. Such an increase is due to a considerable increase in the number of electric units needed for an automobile and because of the mounting of an electronic unit that includes the control circuits for controlling the above-described electric units. Therefore, electrical junction boxes each having connectors formed on a side surface thereof, that is, electrical junction boxes arranged in such a manner that connectors can also be fastened to the side surfaces have been used widely in recent years.
A bus-bar circuit board which serves as the internal circuit of the electrical junction box is typically constructed by stacking a plurality of bus-bars, which have desired patterns, and insulating plates. Successively formed on the bus-bars are tabs that project upward or downward. The bus-bars are, as the connector terminal, respectively introduced into connector fastening portions of the upper and the lower cases.
In order to raise the density of the projecting tabs, i.e., increase the number of tabs and improve the efficiency of disposing the bus-bars, a structure has been employed (refer to Japanese Patent Laid-Open No. 54-168585) in which a parallel tab extending in parallel to the surface of the bus-bar and projecting over an edge of the insulating plate is fastened to a connector housing disposed on the side surface of the case. The parallel tab may be either a plane tab extending from the bus-bar directly or a stepped tab which is cranked at the end surface of the insulating plate. In this case, an alignment of the pitch of a group composed of the parallel tabs to the terminals of the connectors, to which the group is fastened, can be accomplished by changing the height established due to the bending of tabs.
However, the stepped (cranked) tab projecting over the insulating plate encounters the following various problems due to its structure:
(1) Since two portions of the stepped tab must be bent, it is difficult to accomplish an alignment at the front end portion of the tab.
(2) As a result, a predetermined terminal or a connector cannot easily be fastened, therefore requiring additional time to be taken in order to complete the assembling operation.
(3) Since the cranked portion is formed at the end surface of the stacked insulating plate, that is, at the same height and in the same plane, only the bus-bars disposed in the same layer can be subjected to the bending work. Therefore, the tabs cannot freely be projected out.
(4) The developed length of the bus-bar becomes too long and the area of the bus-bar formed by pressing work becomes too large. Furthermore, yield or number of the bus-bars that can be punched out from a thin plate deteriorates.
(5) Structures for projecting and supporting the stepped tabs become too complicated. In addition, a desired circuit of the above-described type cannot easily be designed. Therefore, an excessively large cost is required to manufacture the punching die and the molding die. In addition, the assembling facility is unsatisfactory.
An object of the present invention is therefore to provide an electrical junction box capable of overcoming the above-described problems and structured in such a manner that connectors can also be fastened to the side surface thereof.